Now, it's the completely renovated home to the Bay Area's largest regional government agencies.

The refurbished Bay Area Metro Center reopened in May 2016 at 375 Beale St. in the Rincon Hill neighborhood of San Francisco.

The $115 million remodeling of the eight-story building was no easy task.

Among other things, crews had to cut through 10-inch-thick concrete floor slabs that were installed in 1942 when armored tanks were being built there.

"It was a bullet-proof building. It was tough as nails," said Michael Gilpin, the senior project manager for McCarthy Building Cos., the general contractor on the project. "It was a major challenge."

In the end, the office complex received a complete seismic upgrade and now features an atrium that cuts through all levels, allowing natural light to filter everywhere inside.

That's in addition to an auditorium and a laboratory for the Bay Area Air Quality Management District. Besides the district, the other tenants include the Metropolitan Transportation Commission and the Association of Bay Area Governments.

"I can see the building when I drive in across the Bay Bridge and it's an awesome sight," said Gilpin.

The project itself was incredibly controversial. The agencies decided in 2011 to leave Oakland and buy the 455,000-square foot building for a joint regional headquarters. Oakland officials were upset and civic watchdogs questioned if public agencies should become developers. In the end, the agencies went ahead with the project, buying the site for north of $100 million.

The agencies eventually sealed a lease for 92,000 square feet to tech firm Twilio. Two engineering firms, Degenkolb Engineers and Rutherford + Chekene, have already leased a total of 50,000 square feet.